minecraft-assets/data/minecraft/recipes/gray_candle.json

{
  "type": "minecraft:crafting_shapeless",
  "category": "misc",
  "group": "dyed_candle",
  "ingredients": [
    {
      "item": "minecraft:candle"
    },
    {
      "item": "minecraft:gray_dye"
    }
  ],
  "result": {
    "count": 1,
    "id": "minecraft:gray_candle"
  }
}